Comment by benkaiser
I think the parent may be referring to the fact that safari/webkit will evict all localstorage/indexeddb/caches etc after 7 days of not visiting a site. And apparently this now extends to PWAs making it a pretty big blog to building any infrequently accessed PWA that needs to persist user data locally.
I store my data in the service worker cache, so I guess I'm immune to this issue